Turbine blade shroud fastening



April 1943- c. c. FRANCK 2,315,611

TURBINE BLADE SHROUD FASTENING Filed Feb. 14, 1942 2 Sheets-Sheet 1 a0 83 aa 20 23 aa aa 3 2 19 a2 a3 39 L 5 f 84- 1'7 ATTORNEY April 1943- c. c. FRANCK 2,315,611

TURBINE BLADE SHROUD FASTENING Filed Feb. 14. 1942 2 Sheets-Sheet 2 IN OR CLRRENCE C. RNCK.

BY I IR TORNEY Patented Apr. 6, 1943 TURBINE BLADE SHROUD FASTENING Clarence C. Franck, Swarthmore, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 14, 1942, Serial No. 430,842

2 Claims.

The invention relates to turbine blading and it has for its object to provide an improved method and construction of turbine blades permitting of their connection to a rotor so that full advantage may be taken of the mechanical strength of the structure in resisting forces to which the blades may be subjected and without there being any locked-up stresses in the blading incident to assembly and attachment thereof to form the blade row.

It is common practice to have the blades of a row connected to a. rotor by having inwardlyfacing shoulders formed on the rotor and cooperating with outwardly-facing shoulders formed on the blade roots and to have the blades connected by a shroud or lashing structure. With the shroud or lashing connected, the root shoulders may not bear against the rotor shoulders uniformly; and, in consequence, the blade structure, particularly the shroud or lashing construction thereof, may be overstressed or unevenly stressed when centrifugal forces are developed in the blades. In accordance with the present invention, there is employed a shroud or lashing construction which permits of each blade root shoulder bearing firmly against the cooperating rotor shoulder, whereupon, with this relation established, the shroud or lashing construction is completed without the introduction of any deformation or stress. The improved method, therefore, inherently requires blades each of which is provided with the usual root and with a shroud or lashing element, the shroud or lashing elements of adjacent blades having overlapped portions which are spaced-apart radially to a small extent after initial assembly of the row of blades on the rotor, and the latter is rotated at a speed of about twenty per cent above normal so that the roots and all parts will assume a natural position with all seating or shoulder surfaces firmly engaged to resist forces to which the blades may be subjected. After spinning of the rotor at an overspeed for the purpose just stated, spacer members of suitable thickness are introduced between each pair of lapping portions of the shroud or lashing elements and each pair of lapping portions and the spacing member are secured together.

A further object of the invention is to provide a turbine rotor having a row of blades connected thereto by means of cooperating rotor and blade root shoulders and it has for an object to provide the blades with lapping portions such that, with the blades of the row assembled with the shoulders thereof engaging the rotor shoulders, lapping portions of adjacent blades will be in overlapped and spaced-apart relation together with spacing members arranged between each pair of overlapping portions, each spacing member having a thickness conforming to that of the space, and rivets for connecting the overlapping portions and the intervening spacing elements.

These and other objects are effected by the invention as will be apparent from'the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a fragmentary sectional view of the improved blading;

Fig. 2 is a fragmentary plan view looking down on the shroud construction of Fig. 1;

Fig. 3 is a sectional view taken along the line of IIIIII of Fig.

Fig. 4 is a detail isometric view of the outer end of one of the blades and showing the lapping portions thereof extending in opposite directions;

Fig. 5 is a fragmentary elevational view showing overlapped elements or portions connected to the blades and connected so as to form a lashing for the latter;

Fig. 6 is an enlarged detail view of one of the blades illustrated in Fig. 5 and showing. the lashing in section;

Fig. 7 is a sectional view taken along VII-VII of Fig. 6;

Fig. 8 is a sectional view taken along the line the line VIII-VIII of Fig. 7; and

Fig. 9 is a view similar to Fig. 8 but showing a modified form of lashing.

In the drawings, the blades ll forming a row are secured to the rotor 9 by means of inwardlyfacing rotor shoulders I! cooperating with outwardly-facing shoulders 13 formed on the blade roots l4. While the cooperating shoulders may be provided by any suitable rotor and blade root structure, as shown in Fig. 3, the rotor has a blade groove l5 formed with inwardly-extending annular flanges l6 providing the inwardly-facing shoulders I! and each blade root is formed to lit the groove, the root having laterally-projecting portions ll providing the outwardly-facing shoulders I3. I

The blades are formed with shroud or lashing elements, which, upon assembly of the blades in a row have spaced-apart lapping portions.

In Figs. 1 to 4, inclusive, there is shown a row of blades having a shroud construction, at l9, comprised by lapping portions 20 and II, spacers 22 arranged between the overlapped lapping portions 2| and the blade llb has only overlapping portions 20, the reason for this special construction being to permit of assembly of the last blade lib. Assuming the blade row to be assembled with the exception of the last blade Nb and with the blade Ila and a blade H at opposite sides of the filling opening, then it will be apparent that as the adjacent sides of these blades have underlapping portions, the blade Hb with overlapping portions may be readily inserted to bring the lapping portions thereof into overlapped relation with respect to the lapping portions of the adjacent blades I la and II.

With the blade row assembled, the rotor or disk is rotated at a desired speed above normal, for example, about twenty per cent above normal, the effect of overspeeding being that the blades are constrained thereby each to assume its natural position with its root shoulders; firmly engaging the rotor shoulders.

After overspeeding, spacing members or shims 22 are inserted in the spaces 24, each shim or spacer being individually fitted to its space, and each pair of overlapped portions and the intervening spacer or shim of fitted thickness are secured together by any suitable means, as by a rivet 23.

In Figs. 6 to 9, inclusive, there is shown a structure wherein the lapping portions 20a and 2la, the spacers 22a and the rivets 23a cooperate to provide a lashing construction instead of a shroud construction, as in Fig. 1. Preferably, as shown in Figs. 6, 7, and 8, the lapping portions 2%; and 21a are formed integrally with the blades Ila. In Fig. 9, instead of the lapping portions being formed integrally with the blades, they are connected thereto by welding, that is, the lapping portions 2% and 2!?) are connected to the blades llb by welds, at 25.

The lashing construction shown in Figs. 6 to 9, inclusive, is also arranged to be finally connected after preliminary'ioverspeeding of the rotor, that is, after overspeeding, the spacers 220 are formed to fit the individual spaces between overlapping portions 20a and 2la, after which the overlapped portions and the intervening spacer are riveted together by means of a rivet While the invention has been shown in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What is claimed is: v

1. In a turbine, a row of blades; each blade including a root element and each root element having outwardly-facing shoulders; a rotor carrying the row of blades and provided with. inwardly-facing shoulders for cooperation with the root shoulders; and a shroud construction for the row of blades comprising oppositely-extending lapping portions formed integrally with the tip of each blade and the lapping portions of adjacent blades overlapping in spaced-apart relation with the root shoulders of the blades engaging the rotor shoulders, filler pieces fitting the spaces between overlapped portions, and rivets connecting the overlapped portions and the intervening filler pieces.

2. The method of assembling a blade row structure which comprises providing a rotor having inwardly-facing shoulders, providing blades each of which has outwardly-facing root shoulders and circumferentially-extending. elements having lapping portions, assembling the blades in a rowon the rotor with the root shoulders thereof in opposed relation to the rotor shoulders and with the lapping portions of adjacent blades in overlapped and spaced-apart relation, rotating the rotor at a speed a desired amount above normal speed to cause firm engagement of the blade root and rotor shoulders, providing for the space between each pair of overlapping portions a spacing member whose thickness conforms to that of the space, and fastening together each pair of overlapped portions and the intervening spacing member.

CLARENCE C. FRANCK. 

